<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			* {
				/* CSS3盒子模型 */
				box-sizing: border-box;
			}
			/* 
				宽度：就是width，不再受padding和border影响
			 */
			.d1 {
				height: 200px;
				width: 200px;
				padding: 50px;
				border: solid #00FFFF 10px;
				background-color: #000000;
			}
			
			.d2 {
				height: 100px;
				width: 100px;
				background-color: red;
			}
		</style>
	</head>
	<body>
		<div class="d1">
			<div class="d2"></div>
		</div>
	</body>
</html>
